Different effects of bacterial lipopolysaccharide on superoxide anion production by macrophages from normal and tumor-bearing rats.

Bacterial endotoxins or lipopolysaccharides (LPS) exhibit a wide range of modulatory activities on immunocompetent cells. Among the numerous effects of LPS on macrophages, an enhancement of superoxide anion (O2-) release has been reported. In previous studies carried out on tumor-bearing rats, it was found that several functions of peritoneal macrophages such as phagocytic, microbicidal and antiviral activities were depressed. In this paper we evaluated the spontaneous or phorbol myristate acetate (PMA)-induced production of superoxide anion by macrophages from tumor-bearing rats with respect to controls. Moreover, the effect of in vitro priming with LPS on O2- production by the same cells was studied. It was found that the pattern of superoxide release by macrophages from tumor-bearing rats is significantly different from controls. Preincubation of macrophages from normal rats with LPS enhanced the spontaneous and PMA-induced production of O2-. In contrast, the same concentrations of LPS did not prime macrophages from tumor-bearing rats.